Spehro Pefhany wrote :

> At 06:49 AM 5/27/2005 -0700, you wrote:
> 
> 
> >  A 20MHz clocked PIC would update the PWM counters every 50 cycles
> > * 0.2uS/cycle = 25 uS. The PWM period is 256 * 25uS ~ 6.4mS which
> > translates into a PWM frequency of 1/6.4mS = 156Hz. 
> > Triggering the LED
> >> refresh at this frequency should be fast enough to remove perceivable
> >> flicker.
> 
> Scott, 156Hz is nowhere near fast enough in most cases. You 
> have to multiply
> the minimum "flicker" rate times the number of digits being 
> sequentially muxed...

Now wait a minute...

Wasn't this thread about dimming *individual discrete" LEDs ??
I understod that that was what Dave (remember? He who started
the thread...) was talking about.

Not displays made up from e.g. 7-seg displays, which is another
issue imho...

And, with my limited knowledge, 156 Hz seems just fine for 
dimming LEDs.

Regards,
Jan-Erik.




-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist